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Recognizing Explosive Materials in the Fire/EMS Service, Part 1

May 20, 2024

This article will cover the dangers posed to first responders regarding explosive precursors and improvised explosive devices (IEDs).


Scenario: You and your crew are dispatched to a “still response” in your district for smoke in the area and a loud blast. You are an engine company with a total of four firefighters on the rig today. As you approach the area, you do not see any smoke in the area that has been reported. As you pull up to the scene, you remember that the wind strength/direction is 10 miles per hour coming from the west. The temperature outside is already 70°F at 0900 hours. This information is constantly coursing through your mental schematics because wind strength, wind direction, and temperature affect fire behavior and fire dynamics.

Once your driver locates a safe parking area on the street, you instruct everyone to exit the engine and walk to various homes in the vicinity to investigate. The firefighter assigned the nozzle looks inside a two-story residential structure and notices light smoke. You contact dispatch to give the correct location: 1234 Larry Frost Dr.

You also request that dispatch send the police and another engine, a ladder, two battalions, and a med unit in case there is a working house fire inside the structure. Your crew member stated that he knocked on the door and rang the doorbell but there was no answer. Dispatch states that nobody is answering the call-back number, so you decide to make entry after your driver sets up on a hydrant to secure a water supply. The firefighter assigned the nozzle and the hydrant crew member pull an initial 1¾-inch, 200-foot preconnect attack line to make entry through the front door. You force entry because the smoke inside is getting darker and more turbulent. At this time, the other fire companies begin to arrive on scene.

As you and your crew advance the attack line through the front door, you notice two victims lying on the kitchen floor, unresponsive. You radio this information to the incident commander (IC), who gets the medic crews ready for a patient. Per your standard operating procedures, the backup line crew from the second engine advances another line behind your attack crew.

The ladder company officer and his crew member begin pulling the first victim out of the side door and into the driveway. As the firefighter assigned the nozzle extinguishes the fire in the kitchen, you drag the second victim out of the front door to the medics waiting outside. As water is being put on the fire, your crew stymies the fire’s advancement to the basement and the second floor. The fire is now extinguished, and the first benchmark is met. The ventilation fans are started, and the smoke begins to clear. Your crew and the ladder company conduct a primary and secondary search, which produces no other victims. After the atmosphere is cleared by the battalion captain safety officer, every fire company begins to conduct salvage and overhaul.

During salvage and overhaul, you notice jugs of boiled, concentrated urine on the stove and in milk jugs on the kitchen floor and table. You also find 20 large bags of fertilizer in the corner of the kitchen. On the kitchen counter are 30 bottles of bleach and numerous boxes of fruit drink packets. You also find what appears to be heating tablets used in camping. Upstairs, the ladder company then finds 15 large plastic containers of diesel exhaust fluid (DEF) used in diesel-fueled vehicles. The bathroom contains approximately 50 to 60 empty salon-grade peroxide bottles in the bathtub.

(1) This photo shows two chlorates, four acids, and one peroxide but no metals, with a pressure cooker in the background. Although no metals are present, first responders must be aware that this setup looks out of place. Why would fruit drink packets be near bleach, a cold pack, a bottle of peroxide, and a bottle of acetone? Why would any of these products be near each other except for the peroxide and acetone? The two chlorates are the cold pack, which has ammonium nitrate and the bottle of bleach. The packets of fruit drink powder contain citric acid, and the acetone is an acid. (Photos by author.)

The police and the fire investigations bureau (FIB) are notified because you realize these materials are precursors to making homemade explosives (HMEs). The medics report to the IC that the casualties are alive but have sustained serious burns to their faces, airways, necks, chest areas, and arms. Both patients are transported to the nearest Level 1 trauma center hospital. The other injuries sustained to each patient appear to be blast injuries, mainly to the face and chest region. There are also penetrating injuries and blunt-force trauma. Per the medics and the hospital staff, these injuries are in direct correlation to a blast that occurred on scene. You find damage to the stove/oven; the wall; and the kitchen ceiling, which appears to be incidental to an explosion.

The next-door neighbor informed the police and FIB investigators that she suspects the two injured men were making bombs. She states that she has heard loud blasts at the house in the past and watched them carry in lead pipes, caps, containers of gun powder, large amounts of fertilizer bags, and numerous bottles of bleach. She thinks that they may have been dealing drugs because people had been seen driving up into their driveway at strange times in the night, walking into the house, and then leaving within a few minutes. The FIB investigators and the police research prior calls to this location and state that the people living at this location are under investigation for drug manufacturing and sales as well as illegal firearms sales. As it turns out, there was a blast and small fire at this location two years prior, where an unknown suspect placed a low-explosive device on the front door and lit the device. The device shattered the door and blew it into the structure. No persons were injured at that time.

This article will cover the dangers posed to first responders regarding explosive precursors and improvised explosive devices (IEDs). Every first responder must understand the dangers involved as well as how to respond, where to position our apparatus safely, and how to render care to the injured. The possibility of secondary devices must be factored into the response. I will also cover possible preblast device indicators, explosive categories, explosive precursors, IED components, postblast effects, and blast injuries.

Some facts in the above scenario have been changed. However, they are similar to three investigations in which I was involved. I assisted in investigations where our FIB and the Akron Police Department (APD) were lead investigators. Some other investigations required the assistance of the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF); the Federal Bureau of Investigation (FBI); and the Summit County (OH) Bomb Squad (SCBS) because of the complexities of the investigations and the dangers, respectively. The investigations aspect of these dangerous calls are very important. However, with respect to the scope of this article, I will focus on the dangers posed to first responders.

(2) This is a fully constructed, low-explosive IED that was found in the trunk of our suspect’s car. We alerted the Summit County (OH) Bomb Squad to assist in the investigation and render any devices safe. This device was less than a foot long but approximately one inch wide in diameter. The weight, at the time of the investigation, was unknown. However, I estimate that it weighed seven to eight pounds. This low explosive would exert a tremendous amount of power and cause serious injury and death.

(3) This is a complex trip-wire IED made from a pill bottle. Every component needed to make an IED is present except for the explosive material. The initiator is not considered a full IED since the Christmas tree bulb had not been altered. This is a series circuit with a switch and a power source. Do we have SPICES? We have a switch, which is the clothes pin; a power source (9v); an initiator (Christmas tree bulb); a container (pill bottle); and shrapnel (little bag of pellets on the bottom left). The clothes pin has two metal tack connections so that when the wire is tripped and pulls out from the pin, the metal contacts touch, completing the series circuit. The explosive material was left out for safety and training purposes. This is an inert IED constructed for training purposes only. DO NOT attempt to construct any form of IED at any time or anywhere. It is illegal to construct IEDs.

(4) This is a simple, ordinary toolbox, correct? Could this be used as a carrying device for an IED? Could this be the container needed for a fully constructed IED? To all these questions, the answer is undoubtedly “yes”! (

This fire scenario sounds like a normal house fire in Akron, Ohio. We give a scene size-up, secure water, pull attack lines, rescue victims, and finish the job with no injuries. Basic house fires are high frequency, with moderate to high risk in the city. However, it is rare to stumble across explosive materials, precursors, and devices, even though this reality is becoming more common in various cities and municipalities.

Finding explosive materials that are in the process of being constructed into full IEDs is also rare (at least in Akron). Although explosive devices have been found in the city, their use is on the rise, and we must be ready to spearhead the effort to mitigate the aftermath of blasts. The blast effects from an explosive material and IEDs can cause severe injuries to victims and major damage to critical infrastructure such as what occurred on Christmas Day 2020 in downtown Nashville, Tennessee. On that day, a suicide bomber acted alone as an automated voice instructed people over loudspeakers from his recreational vehicle (RV) to evacuate the area. The bomber parked the RV in front of an AT&T building, causing damage to the building and disrupting subsequent communications. More than 60 structures were damaged, some businesses were temporarily put out of commission, and others never recovered because of the blast as well as COVID-19. There were injuries to civilians and two police officers. The only death was the suicide bomber himself.

An AFD battalion captain is dispatched to suspicious packages, bags, and so on. When responding to these types of calls, we maintain a high index of suspicion. The APD is responsible for incident command for all bomb threats. However, if a bomb or explosive is located, the primary responsibility of incident command, and control rests on the shoulders of the AFD. This same responsibility is also assumed by the AFD if a device has already detonated. The following procedures are followed by our captains when called for a suspicious package or bag:

The identification portion of recognizing explosive materials and devices can be difficult if responders are not trained properly or at all. The scenario above revealed many “red flags” regarding suspicious materials. If a first responder notices chlorates, acids, metals, and peroxides nearby, his index of suspicion should be high that explosive materials are being constructed. Suspicious materials include, but are not limited to, the following:

We must also take into account suspicious behavioral evidence such as the number of items mentioned above. Moreover, 50 cold packs torn open, missing the urea or ammonium nitrate material, should arouse responders’ suspicion.

In the above scenario, boiled, dehydrated, and concentrated urine was found. This is important to note as an investigator since the urine contains urea, which can be used in explosives as a fuel. The construction of explosive materials is relatively simple but very dangerous, especially during the testing phase of the construction. This is a fact because bomb makers have to test their explosive materials for effectiveness and strength. A lot of the injuries to bomb makers will arise in the testing phase and construction of the actual device. If a medical professional, firefighter, or police officer is on the scene of a traumatic event such as an explosion that has rendered the person injured or deceased, it is imperative to investigate that the injuries match the event or story given by the patient, family, friends, or bystanders. A missing hand with severe bleeding would not parallel a story that the injured was simply cooking a steak on the grill. In other words, the patient history of that event must match the injuries encountered.

Suspicious devices can come in many forms such as pipes, letters, bags, cardboard boxes, toolboxes, or anything that can hold or contain an explosive material, and the components could be used as a transportation device. By themselves, these containers would not necessarily cause any suspicious of nefarious intent. Moreover, we must consider the context of the situation and the irregularities that may be noticed. If a person finds a random bag sitting in a bus terminal, would this be considered a suspicious bag or situation? My answer is, not necessarily. However, did the person notice anyone place the bag and then just walk away? Was the person who placed the bag acting anxious? Was this person sweating profusely, looking around for cameras, or asking bus terminal employees strange questions? The totality of the circumstances must be taken into account. Just because someone may be sweating is not—in and of itself—suspicious. However, if the weather is cold and the suspect is not wearing a jacket and he places a bag near people then leaves quickly, this should arouse suspicion.

The FBI states in the article, “National Explosives Task Force Suspicious Package Indicators and Recommended Response Procedures,” the following: “Package bombs, which include letters, parcels, and anything delivered by postal or courier service, are not a new technique and have been used by terrorists and anarchist groups. Many of these bombs are triggered when victims handle or open the packages, although they can be initiated in other ways.” This is why it is very important not to move devices or bags. Remember, recognize the threat, avoid it, isolate the area, and notify the proper entities. The FBI goes on to say, “Package bombs come in a variety of shapes and sizes, and they may look harmless. There are a number of characteristics that may lead you to become suspicious of a letter or package.”

Other information that may arouse suspicion about certain packages and letters includes the following:

As stated in AFD’s SOGs, our responders must turn off all radios, mobile terminal devices, and cell phones because the radio frequencies and cellular emissions can activate the device since the wires can also act as an antenna. An unintentional, remote detonation can occur once these wires catch the frequencies and emissions. The Boston Marathon bombers used frequencies and emissions from a remote-control car’s handheld controller to signal the initiator in the pressure cookers they constructed and placed near the finish line.

The construction of IEDs can range from fully complex, involving blasting caps, to the relatively simple, such as pipe bombs. The ATF has implemented the acronym SPICES (Switch, Power source, Initiator, Container, Explosive material, Shrapnel) for an easy way to remember the components of IED construction. More complex devices will have circuitry implemented such as a series circuit, a parallel circuit, or a series/parallel circuit. There will also be a switch or multiple switches and some type of initiator such as a blasting cap or homemade blasting cap, which uses a heat source like a filament. The power source could come in the form of a battery. The container could be anything that will hold the explosive material, which may be a low explosive such as smokeless or flash powders used in propellants and pyrotechnics, respectively. The explosive materials could also be high explosives used in the military such as C4 or in the commercial realm like dynamite or TNT.

(5) Once opened, we noticed a rocker switch in red on the left, called a “safe-to-arm” switch. In other words, the bomber has other switches within the toolbox that were unseen. Once the bomber sets the device down near the intended target, he can open the box and flip the switch on. When this switch is off, the other switches will not complete the circuit. This is a safety feature so that the bomber can carry the toolbox to the intended target. This would lead an investigator to believe that a motion switch may be inside.

(6) This is a complex IED that has a series/parallel circuit, a power source, a pipe bomb, and three switches. Once the safe-to-arm switch is flipped on, one of the other two switches needs to complete the circuit, depending on which switch will ultimately be activated. There are two ways this device will explode or detonate. The first is motion. If someone picks this toolbox up, the aluminum ball inside of the glass tube will contact the two copper wires inside the glass tube connecting the circuit. If the toolbox is not moved or picked up, the egg timer will eventually make the connection in the circuit when the hands make contact with the nails on the egg timer. This is one of the most complex and sophisticated IEDs in use today. The initiator cannot be seen in the picture because it is inserted into the pipe bomb. There has not been any shrapnel placed in or on the device. This is an inert device with no explosive materials inside the pipe and is being used for training purposes only.

The final facet of SPICES is shrapnel, which is added to a device to increase the lethality of said device. Shrapnel could come in the form of ball bearings, nails, screws, hex nuts, marbles, and so on. This is important for investigators to remember because adding extra lethal objects to a device leads to more probable and severe injuries. Moreover, this shows more intent to effect the demise of human targets. These objects are usually intentionally placed inside or around the explosive material. Legally, this shows a higher level of intent to kill.

Proving the addition of shrapnel to a device may be the difference between a bomber receiving a first-degree murder charge vs. a second-degree murder or lesser charge. Fragmentation is simply pieces and parts of the container, a power source, wiring, an initiator, or objects close to the seat of the blast that have propelled outward but still cause injury and death because of penetrating trauma. Therefore, fragmentation and shrapnel are different from an investigative standpoint; both will cause penetrating trauma and can lead to death even though adding shrapnel to a device will lead to a higher level of probability that penetrating trauma will occur.

An understanding of the “fire tetrahedron” is all that is needed to construct explosives, unfortunately, for the bomber. This is one reason why us good folk need to understand how devices are constructed, including knowledge of all the components.

Knowledge is power and safety in today’s violent world. The fire tetrahedron’s components are a fuel, an oxidizer, a heat source, and a chemical chain reaction. Fuels are usually carbon-based substances such as charcoal, sulfur, gasoline, wood, wax, pepper, cumin, and so on. Oxidizers can be bleach, pool shock, ammonium nitrate, potassium chlorate, and so on, and will have a suffix of -ite, -ide, -ine, or -ate included in the generic name. Heat sources come in many forms and can be easily retained and recalled by using the acronym FISHED (Friction, Impact, Shock, Heat, Electrostatic Discharge).

Friction from twisting an end cap of a pipe bomb on or off produces heat, which can cause an explosion if there is any explosive material residue on the threads of the pipe or caps.

Impact causes heat, which can be noticed when one object strikes another object. The transference of energy produces the heat. Potential energy changes to kinetic energy once the object is sent into motion. The impact produces the heat needed for an explosion or detonation.

Shock from a blasting cap or an improvised initiator produces enough heat to set off a bomb.

Heat from a flame is obvious and can come in the form of a lighter or match. Some explosive materials are so sensitive that heat from ambient air and the sun can cause detonation; this is why some explosive materials such as triacetone triperoxide (TATP) must be stored in the freezer—it preserves the material since TATP degrades rapidly. Other sensitive primary explosives must be stored in water to prevent an explosion.

Electrostatic discharge can be caused from a spark in an electrical outlet or lightning, or it can also be caused from a buildup of minor electrical activity in the body. This is seen when a person shuffles across carpet and touches an object like a doorknob or even a person. The person touching the doorknob will feel the shock, as will the person being touched. The flow of electrons causes the heat, which is why copper and aluminum wiring need a thermal covering and why some cords are not rated to take the voltage and amperage of a space heater, for example. The underrated cord will become hot to the touch and can start fires if left on too long.

Akron Fire Departmental. Standard Operating Guidelines (2022): Section 1500.00 Administration Subdivision; subsections 1555.01-1555.08. (Section 1555.01 revision September 2008).

Department of Homeland Security (DHS). Federal Emergency Management Administration (2000-2010) Incident Response to Terrorist Bombings; PER 230-1. Energetic Materials Research and Testing Center (EMRTC): New Mexico Institute of Mining and Technology, New Mexico Tech. version 3.1.1.

Department of Homeland Security (DHS). Federal Emergency Management Administration (2015) Homemade Explosives: Awareness, Recognition, and Response. Energetic Materials Research and Testing Center (EMRTC): New Mexico Institute of Mining and Technology, New Mexico Tech. version 1.0.

DHS/FEMA (2014) Medical Preparedness and Response for Bombing Incidents: MGT-348/PER-233; TEEX, NERRTC, NMT.

Eastman A and D Flory. (2019) TECC: Tactical Emergency Casualty Care, 2nd Edition. Course Manual; National Association of Emergency Medical Technicians (NAEMT), Jones & Bartlett Learning publisher.

Gerecht R. “Trauma’s Lethal Triad of Hypothermia, Acidosis & Coagulopathy Create a Deadly Cycle for Trauma Patients.” (2014). Journal of Emergency Medical Services (JEMS) April 2014.

NFPA 921. National Fire Protection Association: Guide for Fire & Explosion Investigations; NFPA. (2014). Publications Quincy, MA: 8th Edition.

Springer B and M Verbillion. (2017). March/April: Trauma Reports: Practical, Evidence-Based Reviews in Trauma Care; Volume 18, NO. 2.

United States Bomb Data Center (USBDC). 2016 Explosives Incident Report. Accessed on May 14, 2018, at

USDOJ (FBI/ATF) (2008) Indicators and Warnings for Homemade Explosives Handbook.

JARRED R. ALDEN, M.A., FFII, NRP, is a firefighter/paramedic operations officer for the Akron (OH) Fire Department (AFD). He has worked 19-plus years as a firefighter and 17-plus years as a paramedic and is a member of the Akron Police Department SWAT team’s Tactical Medic program. Alden was previously a member of the rescue/recovery dive team. He has NAUI Dive and Public Safety Dive certifications in open water and dry suit and has worked as an arson investigator and the assistant bureau manager for the AFD fire investigation unit’s bureau. His fire investigations certifications are basic origin and cause and advanced origin and cause. Alden is also a nationally registered paramedic and an Ohio state-certified paramedic. He is ITLS, ACLS, PALS, PITLS, and BLS certified. He is a certified firefighter II through the state of Ohio. Alden has a master of arts degree in applied behavioral sciences from Wright State University and a baccalaureate degree in sociology/criminology from Urbana University. He served as a collegiate professor of sociology at the University of Akron for six years and has presented at FDIC International, JEMS 2019, the Ohio State University Fire/EMS conference, and the Ohio Tactical Officers Association conference.

By JARRED R. ALDENPlanning and Response Considerations for Homemade ExplosivesVehicle-Borne Improvised Explosive Devices: Planning and ResponseResponse to Homemade Explosives(1)(2)(3)(4)SPICES(5)(6)FISHEDFrictionImpactShockHeatElectrostatic dischargeJARRED R. ALDENM.A., FFII, NRP,